The long-term objective of this project is to define the significance of lipid signaling for neuronal survival in ischemia-reperfusion damage associated with stroke. In ischemia-reperfusion damage, phospholipase A2 activation, arachidonic and docosahexaenoic acid release, and the accumulation of prostaglandins, lipoxygenase products, and platelet-activating factor are up-regulated. We will test the hypotheses (a) that PAF, a messenger of NMDA-receptor signaling, when overproduced becomes a mediator of neuronal damage in focal stroke;(b) that ischemiareperfusion activates the synthesis of endogenous neuroprotective docosanoid signaling that has the potential for counteracting pro-inflammatory responses (e.g., PMN activation and proinflammatory gene expression);and (c) that PAF antagonism elicits neuroprotection in ischemia-reperfusion. We will also test a corollary of these hypotheses, that PAF-blocking compounds elicit neuroprotection in ischemia-reperfusion damage, in addition to attenuating PAF-mediated neuronal damage, by up-regulating the expression of neuroprotective genes. We will use mice deficient in PAF receptor to define the significance of PAF in the injured brain. Powerful experimental approaches including LC-PDE-MS-MS lipidomic analysis in combination with transient middle cerebral artery occlusion, immunohistochemistry, and molecular biology will be used to study lipid signaling in experimental stroke. These studies will (a) define signaling and novel neuroprotective mechanisms in ischemia-reperfusion;(b) characterize novel docosanoid signaling;and (c) identify new drug strategies to prevent or limit neuronal cell damage or death in stroke.